Evolution of Silicon nanostructures in silicon nitride matrix due to Ion irradiation

Description: 

The response of in-situ formed Si-nanostructures embedded in Si-rich hydrogenated amorphous silicon nitride matrix to 100 MeV Ni8+ ions irradiation is reported here. Si-rich a-SiNx:H films have been prepared by Hg-sensitized Photo Chemical Vapour Deposition. Presence of elemental Si was confirmed from x-ray photoelectron spectroscopy. The hydrogen content of the films before and after irradiation as measured by elastic recoil detection analysis shows depletion of hydrogen from the irradiated films. Si-nanostructures are examined with cross-sectional transmission electron microscopy. Prior to irradiation, Si-nanostructures are amorphous in nature having partial crystallinity. Irradiation with a fluence of 5 × 1012 ions/cm2 under normal incidence at room temperature leads to dissolution of these Si-nanostructures. However, irradiation with a relatively higher fluence of 1 × 1014 ions/cm2 enhances the nucleation and leads to the formation of amorphous Si-nanostructures in the film. In addition, at the surface a novel effect i.e. partial crystallization of Si-nanostructures along the beam direction is observed. The results are understood on the basis of intense electronic energy loss induced hydrogen loss and consequent rearrangement of the amorphous network under thermal spike formalism of ion-material interaction.

Contact details: 

Dr. Santanu Ghosh, Dr. G. V. Prakash, Prof. Pankaj Srivastava and Dr. Sarab Preet Singh

Department of Physics

santanu1[at]physics.iitd.ernet.in